Google, Yahoo, MSN and the closing traffic gap

Over at digg I found a link to Eric's Tech Articles where he has been watching the traffic to Google and MSN getting closer for the past year or so. He is using Alexa Figures.

Quote:
MSN almost seems to be decreasing, as Google is shooting right up there. Looking at the current growth trends, my guesses are Google will surpass MSN sometime late November or early December.

He also has a graph showing that Yahoo are staying flat since June and Google are moving up to meet them. It is an interesting view.

- Y! MyWeb

But how relevant is the

But how relevant is the data? After all, aren't people who are using Google more likely to use Google's toolbar (and hence deflate the Alexa figures for Google) and those using MSN are more likely to use the Alexa toolbar (and hence inflate the Alexa figures for Google)?